In general, a reciprocating steam engine produces rectilinear motion in a piston by supplying high-pressure steam to a cylinder. It then changes the rectilinear motion into rotary motion using a crank unit and rotates a driveshaft. A reciprocating steam engine also reverses the rectilinear motion direction of the piston using the inertial force of a flywheel installed at the crank unit, and discharges steam from the cylinder.
However, conventional reciprocating steam engines operating with a crank unit have several drawbacks. First, they cannot efficiently change the rectilinear motion to rotary motion because energy losses occur in the crank unit when the piston direction is reversed. Second, the rotation of the driveshaft pulsates when steam is discharged from the cylinder to the atmosphere. Third, the flywheel increases the engine weight and the crank unit complicates the engine construction.
This application modifies the crankless reciprocating steam engine with double cylinders, described in Japanese Patent Laid-Open No. 2005-331098, to resolve the above drawbacks. In this engine, the rear chambers of two cylinders communicate with each other using a connecting pipe, and high-pressure fluid is alternately introduced into front chambers of both cylinders. When each piston of the two cylinders reciprocates, the two engaged racks alternately reciprocate. A saw-toothed wheel gear, engaged with the two racks, rotates in both directions. Such two-way rotary motion is transmitted to the driveshaft as one-way rotary motion.
In the above construction, when the motion direction of the piston is reversed, the energy losses become much smaller compared to those of a crank unit. Pulsations in the driveshaft rotation can be prevented because steam is discharged from one cylinder due to the steam pressure introduced into the other cylinder. In addition, a reduced engine weight and simplified engine structure can be achieved because the flywheel and crank unit are unnecessary.
The invention disclosed in Japanese Patent Laid-Open No. 2005-331098 provides a rotary diverter valve installed in the high-pressure fluid path as a means of alternately supplying high-pressure fluid to two cylinders. The rotary diverter valve includes a cylindrical valve that rotates freely, two pipes that are inserted into the path for the high-pressure fluid, and two control levers extending in the radial direction of the cylindrical valve. When the two racks alternately reciprocate, a rod installed in each rack reciprocates in engagement with the rack, and alternately presses the two control levers of the rotary diverter valve. The diverter valve rotates in the forward direction when one control lever is pressed, and in the reverse direction when the other control lever is pressed. By alternately changing the rotational position of the valve, the connection state of the two pipes changes. In other words, when the valve is in its first rotational position, high-pressure fluid is introduced into the first cylinder through the first pipe, while at the same time, fluid is discharged from the second cylinder through the second pipe. When the valve is in its second rotational position, high-pressure fluid is introduced into the second cylinder through the second pipe while fluid is discharged from the first cylinder through the first pipe.
The rotary diverter valve alternately changes its rotational direction, interworking with the two alternately reciprocating racks. By changing the rotational direction, all rotation energy in the valve is lost, rather than conserved as an inertial force, resulting in a substantial reduction in engine efficiency.